Viscosity characterization, polymer

Polymer Viscosity Characterization by Size Exclusion Chromatography... 

Table I provides an overview of general reactor designs used with PS and HIPS processes on the basis of reactor function. The polymer concentrations characterizing the mass polymerizations are approximate there could be some overlapping of agitator types with solids level beyond that shown in the tcd>le. Polymer concentration limits on HIPS will be lower because of increased viscosity. There are also additional applications. Tubular reactors, for example, in effect, often exist as the transfer lines between reactors and in external circulating loops associated with continuous reactors.

Low-molecular weight chains do not experience enough shear force to induce scission. Watson et al." demonstrated (by the intrinsic viscosity characterization of masticated NR) that the limiting molecular weight for the shear-induced degradation is in the order of 0.7-1.0 X 10 Frenkel independently speculated that shear-induced cleavage occurs near the midpoint of the polymer chain. 

Often in hyperbranched polymers obtained via SCVP, it is not possible to determine the DB directly via NMR analysis. Therefore, other methods, for example, viscosity measurements and light-scattering methods have to be used to confirm the compact structure of a hyperbranched polymer. Such characterizations of hyperbranched (meth)acrylates will be discussed in the next section. 

The ratio of extensional viscosity r e to shear viscosity r s is known as the Trouton ratio, which is three for Newtonian fluids in uniaxial extension and larger than three for non-Newtonian fluids. For a viscoelastic fluid such as a polymer in solution, the uniaxial extensional viscosity characterizes the resistance of the fluid... 

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

The polymers were characterized by gel permeation chromatography (G.P.C.), membrane osmometry, intrinsic viscosity, and H-NMR spectroscopy. 

The molecular weights and molecular weight distributions of lower molecular weight polymeric flocculants are determined by viscosity measurements. High molecular weight acrylamide-based polymers are characterized by light scattering techniques. 

The dynamic viscosity and storage modulus of the melt polymer can characterize (1) the degree of dispersity (i.e., intercalation) of the nanocomposite polymer [1,2], (2) the dripping tendency in mesoscale or large-scale fires [3,4], and (3) the structure of the char layer formed during pyrolysis in mesoscale or large-scale fires [5-7]. 

Polymers that are soluble produce solutions with useful and sometimes unusual properties. The solutions of high molar mass polymers are characterized by having relatively high viscosities. Viscosity is dependent upon molar mass, concentration, and temperature. Polymers are useful in many commercial products because of their relatively high viscosity. 

Polymerization of these bisdichloromaleimides was carried by nucleophilic displacement of chlorine with 9,9-bis(p-aminophenyl)fluorene. The resulting polymers were characterized by IR spectroscopy and reduced viscosity measurements. Anaerobic char yields of these polymers at 800°C ranged from 55-60%. In presence of air, a complete loss of weight was observed between 600-650 C. Thermal cross-linking of these polymers was also investigated. 

Hence, for a better and more adequate picture, polymers are characterized by all three average figures—weight-average, number-average, and viscosity-average. Some particular examples will be given below in this book. 

The cone-and-plate and parallel-plate rheometers are rotational devices used to characterize the viscosity of molten polymers. The type of information obtained from these two types of rheometers is very similar. Both types of rheometers can be used to evaluate the shear rate-viscosity behavior at relatively low vales of shear rate therefore, allowing the experimental determination of the first region of the curve shown in Figure 22.6 and thus the determination of the zero-shear-rate viscosity. The rheological behavior observed in this region of the shear rate-viscosity curve cannot be described by the power-law model. On the other hand, besides describing the polymer viscosity at low shear rates, the cone-and-plate and parallel-plate rheometers are also useful as dynamic rheometers and they can yield more information about the stmcture/flow behavior of liquid polymeric materials, especially molten polymers. 

Polymer solutions were characterized for conductivity, zero shear rate viscosity ( /o), and surface tension prior to extrusion. The extruded polymer was characterized for the presence of residual solvent and pyridine using Fourier Ti ansform Infrared Spectroscopy (FTIR). As a complimentary technique, CHN elemental analyzer was used to determine if any pyridinium acetate residue remained (based on detecting nitrogen) in the extruded polymer. For the latter, PCL films were cast from the 15% solution containing 0%, 0.5%, 1%, 2% and 5% pyridine. 

The resulting linear polymers were characterized by TGA, DSC, inherent viscosity measurements, and mechanical properties as shown in Tables 4.18 and 4.19. 

As it is known [9], polymer viscosity at viscous flow depends on relative fluctuation free volume value, which can be estimated according to the Eq. (2.19). In Fig. 6.3 the dependence of parameter characterizing polymer... 

The polymers were characterized by their compositions, intrinsic viscosities, crystallinities and nascent morphologies. Copolymer compositions were measured by IR spectroscopy. Samples were prepared by hot pressing about SOmg.of polymer between aluminium foil at 170 C and 100 kg x cm pressure during 60 s. After removal from the press, they were water-cooled to ambient temperature for about 5 min. Films of approximately lOOp thickness were annealed at 106 C under N2 for 168 h. in sealed tubes. The hexene contents (C ) in mol % were determined by calculation of the 3<> bion ratio and with... 

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